Various laser systems are known in the art. For example, Schlüter, U.S. Pat. No. 6,285,703, entitled “Laser Resonator,” discloses a particular annular CO2 laser with a coaxial discharge structure. Fox, et al., U.S. Pat. No. 4,359,777, discloses that to obtain a high efficiency gas laser which utilizes transverse electrical excitation of a laser gas medium, the excitation energy should be applied to only the optical mode volume of the laser mode.
Broderick et al., U.S. Pat. No. 6,198,759, describes a narrow gap laser operated in the free space mode. Thus, the Broderick, et al. patent notes that the electrodes form a gap large enough to avoid the waveguide mode and have a curved surface so that inner electrode gap decreases from each end towards the center of the laser cavity so as to form the shape of the fundamental transverse mode of the naturally occurring laser beam for the set of mirrors to be used. However, such a device can still support spurious transverse reflections that can reduce the overall efficiency and beam quality.